Cosmic Velocity - First to Velocity of Light in Vacuum

The first cosmic velocity (escape velocity from Earth's surface to orbit) is approximately 7,900 m/s (7.9 km/s), the minimum speed needed to achieve Earth orbit.

v₁ = √(GM/r) where G is gravitational constant, M is Earth's mass, r is Earth's radius. Approximately 7.9 km/s.

To km/h: × 3,600. To mph: × 17,672. 7.9 km/s = 28,440 km/h = 17,672 mph.

Minimum speed for satellites, space station orbit, and low Earth orbit (LEO) calculations.

ISS orbits at ~7.66 km/s. Below this speed, you fall back to Earth. Above it, you stay in orbit (if horizontal).

Confusing with escape velocity (second cosmic velocity, 11.2 km/s) — orbital velocity is lower.

Remember: ~8 km/s for orbit, ~11 km/s to escape. v₁ is minimum for orbit, not escape.

The speed of light in vacuum is a fundamental physical constant, exactly 299,792,458 meters per second. It's the maximum speed at which all energy, matter, and information can travel.

c = 299,792,458 m/s exactly (by definition). In km/h: 1,079,252,848.8 km/h. In everyday units: about 300,000 km/s or 186,282 miles/s.

To km/h: × 3,600 × 0.001. To mph: × 2.237 × 10⁻⁶. Often expressed as multiples: 0.5c, 0.9c, etc.

GPS satellite timing (requires relativistic corrections), fiber optic communications, laser ranging, and astronomical distance measurements (light-years).

Light from the Sun takes 8 minutes 20 seconds to reach Earth. Nothing with mass can reach c. Cherenkov radiation occurs when particles exceed light speed in a medium (not vacuum).

Thinking light speed is instantaneous — it's not. Confusing speed in vacuum (c) with speed in glass/water (slower). Forgetting relativistic effects near c.

Remember c ≈ 300,000 km/s (simplified). Nothing goes faster. Used in E=mc². Light takes 1.3 seconds to reach the Moon from Earth.